Hydrocyanation



Dec. 28, 1954 R. L. HEIDER ET AL HYDROCYANATION Original Filed Aug. 23,}951

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FIGURE l 2 Sheets-Sheet l SYSTEMI HCN-DIMETHYLFORMAMID FP-l4 I FREEZING POINT:- COMPOSITION E(DMF) .4 .6 MOLEFRACTION DMF FIGURE 2 FREEZING POINT-COMPOSITION SYSTEMI HCN-DIMETHYAGETAMIDE (DMAG) .4 .6 MOLEFRACTION DMAC INVENTOR RUDOLPH L. HEIDER HARRY M. WALKER ATTORNEY Dec. 28, 1954 R. L. HEIDER ETAL 2,698,337

HYDROCYANATION Original Filed Aug. 25, 1951 2 Sheets-Sheet 2 LIQUID-VAPOR EQUILIBRIUM DATA SYSTEM: HON-DMF FIGURE 3 I60 I40 VAPOR(EXPER|MENTAL) l 2 O VAPOR (RAOULTS LAW) IOO s E LIQUID 8 (EXPERIMENTAL) N LIQUID 4O (RAOULTS LAW) o I I l l o 20 4o so 80- I00 MOLE /o HCN IN DMF INVENT OR RUDOLPH L. HEIDER HARRY M. WALKER ATTORNEY United States Patent HYDROCYANATION Original application August 23, 1951, Serial No. 243,212. Divided and this application September 13, 1952, Serial No. 309,532

8 Claims. (Cl. 260465.8)

The present invention relates to a process of adding hydrocyanic acid to unsaturated organic compounds and comprises the process of hydrocyanating organic com pounds such as olefinic and acetylenic compounds by the use of certain hydrocyanic acid-containing systems.

The object of the invention is to provide an improved method of hydrocyanating unsaturated organic compounds. Other objects of the invention will be apparent from the description which follows hereinafter.

Many processes of hydrocyanating unsaturated organic compounds are known in the art. The process of the present invention is novel and by its use the reaction between the unsaturated organic compound and the hydrocyanic acid is facilitated, the reaction period is shortened and certain hydrocyanation reactions can be controlled so as to proceed with a diminished formation of undesirable by-products.

The advantageous results of the present invention depend from the discovery that systems of hydrocyanic acid and N,N-dimethylformamide or N,N-dimethylacetarnide, contain molecular complexes of the acid with the amide, and that the presence of such complexes in said systems permits hydrocyanation at temperatures which are higher than those which can be employed in the absence of the molecular complexes.

The term system may be defined as the compounds, eutectic compositions, or the mixtures and solutions existing at equilibrum between molecules of hydrocyanic acid and N,N-dimethylformamide or N,N-dimethylacetamide.

The presence of molecular complexes in mixtures of dimethylformamide-hydrocyanic acid or dimethylacetamide-hydrocyanic acid has been established by a variety of observations. For example, when hydrocyanic acid is passed into dimethylformamide or dimethylacetamide, considerable evolution of heat occurs. Similarly there is considerable evolution of heat when dimethylformamide or dimethylacetamide is added to the acid. Actually when one mole of hydrocyanic acid is mixed with one mole of dimethylformamide or with one mole of dimethylacetamide, the heat evolution is 1158 calories and 1396 calories, respectively.

The presence of complexes in the hydrocyanic acidacylamide systems has also been established by determining the freezing point characteristic thereof and by obtaining liquid-vapor equilibrium data. In the appended drawings, Figures 1 and 2 present freezing point data and Figure 3 presents the liquid-vapor equilibrium data.

Figure 1 shows the freezing point range for the system: hydrocyanic acid-dimethylformamide and indicates a molecular :complex of the type 2HCN.HCON(CH3)2 having a freezing point of approximately minus 72.7 C. This material is a crystalline compound. Figure 1 also illustrates the freezing points of compositions containing varying proportions of the molecular complex togather with one or the other of its constituent substances. The presence of two eutectics in the system is indicated by the drop of the freezing point curve to the minimum values shown on the diagram.

Figure 2'shows the freezing point range for the sys- -.tem: hydrocyanic acid-dimethylacetamide and indicates molecular complexes of the type 2HCN.CH3CON(CH3)2 and of the type HCN.CICON(CH3)2. These complexes have freezing points of minus 7 1.6 C. and minus 75.7" C., respectively, and are crystalline compounds. Figure 2 also illustrates the freezing points of compositions containing varying proportions of the complexes together with one or the other of its constituent substances. The presence in the system of three eutectics is indicated on the freezing point curve.

Figure 3 illustrates liquid-vapor equilibrium data for the system hydrocyanic acid-dimethylformamide (DMF) Curves derived from experimental data and the theoretical Raoults law curves are plotted. These data indicate that the system possesses considerably higher boiling points (lower vapor pressures) than is predicted by Raoults law. Accordingly reaction systems may be employed at higher temperatures than is possible with hydrocyanic acid alone. Since these complexes form in the presence of water or inert organic solvents, aqueous hydrocyanic acid or solutions of this acid in such inert solvents as benzene or ether may be used for their preparation. Determination of the freezing point depression caused by small concentrations of hydrocyanic acid and dimethylformamide or dimethylacetamide in benzene indicates appreciable complex formation at the freezing temperature. Formation of molecular complexes of hydrocyanic acid with dimethylformamide or dimethylacetamide occurs over a wide range of temperature and the complexes exist at temperatures which are above those generally used in hydrocyanating reactions.

In the methods heretofore used for the hydrocyanation of unsaturated organic compounds, the unsaturated compounds are subjected to the action of gaseous or liquid hydrocyanic acid or to solutions of the acid in various sol vents which are either miscible or immiscible with the unsaturated compound; for example, in the manufacture of acrylonitrile, acetylene and hydrocyanic acid are passed into aqueous solutions of cuprous salts while in the hydrocyanation of methyl vinyl ketone, reaction of the olefinic compound with hydrogen cyanide is eifected in the presenceof essentially neutral diluents such as, benzene, toluene, pentane, ether, methylene chloride, etc. In the practice of the present invention the hydrocyanic acid is added to the unsaturated compound in the form of the hydrocyanic acid-acylamide solution described above. The hydrocyanic acid-acylamide systems may also be formed in any order, that is, the acylamide may be added to the substance to be hydrocyanated and thereafter hydrocyanic acid added to the resulting solution or mixture or the reverse procedure may be employed. For certain types of reaction, one of these alternatives may be more advantageous than another.

The process of the invention is applicable to the hydrocyanation of a wide variety of compounds having unsaturation, e. g., mono-olefinic or diolefinic hydrocarbons, acetylene, acetylenic hydrocarbons, saturated or unsaturated aldehydes, ketones, quinones, azomethines, etc.; but it is particularly useful in the addition of hydrocyanic acid with an unsaturated compound selected from the class consisting of (1) acetylenic compounds are generally compounds having an activating group attached to the unsaturated carbon atom. The unsaturation may be olefinic or acetylenic. Examples of compounds in which the activating group is the CN radical are acrylonitrile, and l-cyanobutadiene-1,3. Compounds containing the C=O radical attached to the unsaturated carbon atom are e. g. ketones such as methyl vinyl ketone or mesityl oxide, aldehydes such as acrolein, crotonaldehyde, a,B-mono-olefinic unsaturated acids and esters thereof such as acrylic acid, methyl methacrylate, maleic acid and diethylfumarate, and esters of unsaturated alcohols such as vinylacetate and vinylformate. Unsaturated compounds in which there is attached to at least 1 unsaturated carbon the radical --CH=Cl-l are dienic or polyolefinic hydrocarbons such as butadiene, cyclopentadiene, hexadiene, etc. The present process is Patented Dec. 28, 1954 3 especially-to be preferred'when working with low boiling materials andparticularly withunsaturated compounds selected from the class consisting of a,13-monoolefinic nitriles, ketones and carboxylates of from 3 to 6 carbon atoms.

"lhe; hydtocyanation: process. can be: conducted: under atmospheric or increased pressure, and im mQSB a eS it; is advantageousto; promote thereactionbyheating; The process can be; condu'ctecb either: as; a, batch or; a: con tinuons operationa. Qatalysts. such as. inorganic: alkalisg. metals, and metallic.- salts; may be used to facilitate the: addition: reaction. "Ehe. unsaturated compounds. may be. dissolived in: a solvent therefon. or they may be. reacted inthe: absence; of. a. solvent. Catalytic. materials may be present if. desiredz.

The: present process and the. beneficial. eifects of; the. present hydrocyanic acid-acylamide systems: willtbemore specifically described: by reference to the production; of! succinonitzrile;

Preparation: of succinon'itrilciby reaction: ofi acrylonitrile'. with. hydrocyanic acid is described. in: S; Patent No. 2,434;6.06' and also. in: German Patent No; 7075852; In these prior processes gooth yields of succinonitrile. were obtainable. only by conducting: the. reaction for at: least aboucthree hours and so'mctimesior more than124ihours'. The long reaction times employed: were necessitated by: reason of? thevolatility of the hydrocyanic acid, making it difiicult: to: retain; the said hydrocyanic acid in the liquid. phase; The: present invention provides a method for; substantially decreasing: the reaction time without decreasing the yields of succinonitrilethereby obtained.

We have. found that: by employing a system ofhydrocyanic acich and dimethylformamid'e: or dimethylacetamide: a. substantially quantitative: yield-of su'ccinonitrile: may be obtained in a. considerably shorter period or time than was. possible in prior art processes;

Briorart processes employing: solvents or diluent's. in this reaction could not result, in ashort reaction time because of the absence of: compounds. capableof forming association complexes with hydrocyanic" acid:

It has been ascertained" that the N',N-di1nethyl'acyl'- amides do not act as catalyzersfor the reaction intheordinary'sense of theterm. It is, accordingly, necessary that the reaction betweenacry-lonitril'e and hydrocyanic; acid: be catalyzedby alkaline catalyst, for example; such asthose disclosed by the prior art patents referred toabove. Asalkaline catalysts useful for the present reaction we prefer the organic-bases such as the secondary and tertiary al-kylamines, quaternary ammonium hy-- droxides, sodium or potassium hydroxides; sodium or potassium cyanide, etc.

The-present invention canbe adapted for either batch wise or continuous operation. When operatingin a batch wise manner, the reactants can'be mixed together in any convenient order. In-order words, the dimethylacylamide HCN system, since it is instantaneouslyformed upon mi-xing; of the ingredients, may be first formed in the reaction zone atthe time the reactants are initially brought together. On the other'hand, it? desired; the dimethylacyl amide-HCN- system. may be firstformed; in aseparate operation and the acrylonitril'e' added theret'oz The alla line catalyst may be-added to the reaction vessel contain-- ing' the reactants or it may be added to either reactant prior to mixing.

When operating in a'continuous manner, the same prac tice may be followed. However, in this case it'isgenerall-y' more convenientto prepare a mixture of acryl'oni-"trile'and hydrocyanic acid in the desired" proportions one vesseland: in a second vesselprepare a mixture of the'dimethyl acrylamide and the: alkaline catalyst; Appropriatequantities of the contents of eachvessel are passed into-a tubular reaction vessel which is. surrounded by a heating or cooling jacket. The reactionvessel is of such size as to: provide a sojourn time on the order 055 to minutes, while the capacity of the jacket is of such capacity as to. maintain. the temperature of the reaction between 70 andi20 C. The reacted mixture is-discharged'from the re action zone into a still for recovery of the product in the usual manner.

The reactants may be employed in equimolar' proportions, although in the event that one of the reactants is employed in an excess over equimolar proportions with respect'to theother; recovery of such excess can beeffected at the conclusion of the process. Since the hydrocyanic acid is the most volatile reactant employed and its recovery from the reaction product somewhat ditficult as wellas hazardous,- it' is preterredthattheacrylonitrile' be employed in a slight excess with respect to the hydrocyanic acid supplied. in this manner the hydrocyanic acid is substantially completely used up, so that any difiiculties attending the working up, and.,r.ecovery of this reactant are avoided.

The quantity of. the; dimethylacylamide employed is also somewhat variable; however, for best results there should;be suflicientaoi thismater-ial present in the initial reaction: mixture. to form.- the. above described: associated complex. In other. words,. there should bepresent: at least one half mole of dimethylacylamide per mole of hydrocyanic acid present. Onthe other hand; there may be present up to as much as15-' to 10molesof thedimcthylacylamide per mole of hydrocyanic acid employed, since the former compound, is recovered fromlheproduct without significant loss.

The amount of catalyst employed may be from 1% to 20% by weightrof; the reactionzmass, the-amount employed; not being. criticak provided: that at least; catalyticamounts. are-present. The: catalytic. material is alsore covered, without; significant loss; and, at course, may be reintroduced. into. the reaction; vesseli for catalysis of a: subsequent; batcht.

The following examples: illustrate: this: invention:

Example 1 One; hundred grams of dimethylformamide and 29- g; of tri'ethy-lamine were placed in a'flask andi 106g: (2 moles) of: acrylonit-rile and 54 g: (2 moles) of-hydrocyanicacid were introduced into. an ice-cooled dropping funneli The contents of thefi'askwere heatedto-80- C. andthe hydro cyanic-acrylonitrile mixture was. dropped in uniformly during 45 minutes. The-reactionwas-exothermic frorn'the' start and constant use of the ice bathwas requiredtwkecp' the temperature at 80;-90-" C. No refluxing; of hydrocyanic aci'ct occurred; The mixture was stirred for an additional 40' minutes; however; it, was apparent that the reactionhad been completed after-about 15- minutes. Distillation or" the reaction mixture through a 6" Vigreux' column yielded 100 g: of-amixtureof dimethylformamide and triethylamine and- 14419 g: of succinonitrile. The yield was 90.5% based on either acrylonitrile or'hydro? cyanic acid and therecovery of. solvent was 99%".

Example 2:

A mixture, consisting of, 2,39 moles; of acrylonitrile; and 2.0v moles of hydrocyanic acid waszplaced: in one. vessel while in another. vessel. was placed: 180.6. g,v ofi dimethyl formamide, and 7.3: g. oftriethylamine. The. aho e liquids; were fed; into: atubular reaction: vessel: oi? such size an to-provi'dea sojourn time therein of 1-1 minutesv A'ewatezr jacket surrounding the reactor maintained; the empera. tureof the.reaction;mixture,betweenJO and Q Th reaction mixture was discharged from the tuberintoratdia tillation vessel andthen-d-istilled. Distillatiomof the mix? ture. yielded. a light fractionrboiling; below." 1.42: (2.. and; consisting of acrylonitrile, triethylanrine; and; dimfitl-yh formamide andthe succinonitrile: traction; (13;... 12;, 16,75- 172, C./40 nnn. pressure); amounting, I01 Lil-.6. a; The yield. or succin'onitrile was 94.6%. The-recoveryot we reacted;v acrylontirile, the t-riethylamine and; dimfltthy lformamide was. substantially 1.60%

Example 3 bimethylformamide (16321 g.) and" a recovered light fTQIGUOXl (51.2 g.) from a previous'runcontaining'acryh omit-rile 2010 g;)*, triethylamine- ({l 4l7 gz}, anddimethyl formamide- 1633 g:) werefed to the reactor where they mixed with a stream containing 2' moles each of. hydrocyanicacid and acrylonitril'e; The rate of feeding was," such asto afford an average contact time off 1014 minutes, in the reactionvessel. Temperatures in the reactor were 78-88- C. duringthe run. Di'stillfationoffthe reactor effiiient yielded: (1) light ends 4416 g., (2') dimethylforttr' amide, 157.5 and 3 succi'nonitrile 153.5 (95.9 1-. The recovery of excess acryloni'trile.tri thylarniueand dimethylformamide. was substantially- 09%., uni demonstrates the practicability of recycling the excess acryionitrile; triethlamine anddimethylformamide;with no reduction in yield 'or materi'aI recovery; As, many as sex/en.

successive runs were made with little'or no make-up of these materials.

Example 4 Dimethylformamide (recovered from a previous run) 52.0 g. and a light ends fract n (60.8 g.) from a previous run estimated to contain acrylonitrile (21.0 g.), dimethylformamide (20.0 g.), triethylamine (17.0 g.) and water (20.8 g.) were fed together with a stream containing equivalent amounts (2 moles each) of hydrocyanic acid and acrylonitrile to the tubular reactor. The feed rate was such as to give a contact time of 10.4 minutes. Temperatures along the reactor were 7891 C. at all points during the run. Distillation of the effluent yielded: (1) light ends 52.1 g., (2) solvent 58.9 g. and (3) succinonitrile 152.1 g. (95.1% The recovery of excess acrylonitrile, triethylamine and dimethylformamide was 98.5% (without corrections for losses). This run demonstrates that considerably less dimethylformamide (0.5 moles per mole of HCN) can be used without loss of its beneficial effects. However, some boiling of HCN occurred before the reactor was entirely filled with liquid. Recycle materials were also used in this run.

Example 5 This run was essentially identical with the previous one except that dimethylacetamide (72.6 g.) and triethylamine (17.0 g.) were charged to the solvent-catalyst feed vessel. The yield of succinonitrile was 93.0% and the recovery of light ends and dimethylacetamide was 96.3%.

The use of the hydrocyanic acid-dimethylfonnamide or dimethylacetamide systems for the hydrocyanation of organic compounds gives improved yields in shorter reaction times generally. Thus, the present systems may be used to good advantage in the manufacture of acrylonitrile from acetylene and hydrocyanic acid, in the preparation of 1-cyano-1,3-butadiene and 2,3-dicyano-2-butadiene from vinyl acetylene and hydrocyanic acid, in the preparation of lactonitrile acetate from vinyl acetate and hydrocyanic acid, the preparation of l-cyano-cyclohexyl acetate from l-cyclo-hexenyl acetate and hydrocyanic acid, the preparation of levulinonitrile from methyl vinyl ketone and hydrocyanic acid, the preparation of ethyl Z-cyanoacrylate from ethyl propiolate and hydrocyanic acid, etc.

This application is a division of copending application, Serial Number 243,212, filed August 23, 1951.

6 What is claimed is: l. The process of facilitating reactions involvlng the addition of hydrocyanic acid to an a,,9-mo11o-olefinic aliphatic nitrile which comprises contacting said nitrile with the system: HCN-RCON(CH3)2 in which R is selected from the class consisting of hydrogen and the methyl radical.

2. The process of facilitating reactions involving the addition of hydrocyanic acid to an a,;8-mono-olefinic aliphatic nitrile which comprises contacting said nitrile with the system: HCN-HCON(CH3)2.

3. The process of facilitating reactions involving the addition of hydrocyanic acid to an a, 8-mono-olefinic aliphatic nitrile which comprises contacting said nitrile with the system: HCN-CH3CON(CHs)2.

4. The process for producing succinonitrile which comprises contacting acrylonitrile with the system: HCN-RCON(CI-La)2 in which R is selected from the class consisting of hydrogen and the methyl radical.

5. The process for producing succinonitrile which comprises contacting acrylonitrile, in the presence of an alkaline catalyst, with the system: HCN-HCON(CH3)2.

6. The process for producing succinonitrile which comprises contacting acrylonitrile, in the presence of an alkaline catalyst, with the system: HCN- CH3CON(CH3)2.

7. The process of producing succinonitrile which comprises treating acrylonitrile, in the presence of an alkaline catalyst, with hydrocyanic acid while dissolved in an amide selected from the group consisting of dimethylformamide and dimethylacetamide.

8. The process of producing succinonitrile which comprises treating acrylonitrile, in the presence of an alkaline catalyst, with hydrocyanic acid while dissolved in an amide selected from the group consisting of dimethylformamide and dimethylacetamide at a temperature in the range of from about C. to about C.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,460,603 Semon Feb. 1, 1949 2,547,686 Brockway Apr. 3, 1951 

1. THE PROCESS OF FACILITATING REACTIONS INVOLVING THE ADDITION OF HYDROCYANIC ACID TO AN A,B-MONO-OLEFINIC ALIPHATIC NITRILE WHICH COMPRISES CONTACTING SAID NITRILE WITH THE SYSTEM: HCN.RCON(CH3)2 IN WHICH R IS SELECTED FROM THE CLASS CONSISTING OF HYDROGEN AND THE METHYL RADICAL. 